The dairy industry is producing increasing quantities of lactoserum which is a liquid phase obtained after the precipitation from milk (by the addition of rennet or acid) of the casein used in the production of cheese. Lactoserum has the following average composition.
______________________________________ water 960 g lactose 35 g ash 4 g potassium 1 g sodium 0.50 g riboflavin 1.4 mg niacin 1 mg thiamin 0.3 mg calcium 0.25 mg phosphorus 0.20 mg vitamin A 100 UI proteins traces ______________________________________
French Pat. No. 71 27592 describes a process for the preparation of galactose from a solution of lactose such as lactoserum. In this process, it is first of all necessary to bring the lactose concentration of the lactoserum to between 5 and 15%, then to subject the solution obtained to acid hydrolysis, followed by adjustment of the pH of the solution to a value between 3 and 6. The solution, which now contains glucose and galactose emanating from the hydrolysis of lactose, is fermented by a strain of fermenting yeast which assimilates the glucose but not the galactose. The yeasts are then separated from the medium containing the galactose by centrifuging.
The process involves numerous operations. It is possible by chemical hydrolysis to treat lactose solutions with a concentration of from 5 to 15%, whereas crude lactoserum only contains approximately 3.5 % of lactose. As a result, it is difficult to obtain the complete removal of glucose in the fermentation towers. In addition, since the operation is carried out without growth, it requires particular sterility conditions.